readimagefile

(tmp_for_tar/imgio/readimagefile.m)

Function Synopsis

[im, isPpm, maxval] = readimagefile (fname, force_gray)

Help text

 [im, isPpm, maxval] = readimagefile(fname, force_gray)

 fname      : string : name of image file.
 force_gray : flag   : (opt) if true, the returned image is a gray level
                       image, even if the file contained a color image.
                       (default: false) 
 im         : matrix : an image.  Note, that if force_gray == false, the
                       image might by a PPM representation of the image.
 isPpm      : flag   : 1 : `im' is in PPM format.
                       0 : `im' is a graylevel matrix.
 maxval     : int    : Maximum luminosity level (usually 255)

 See also: readpnm, readfi, readjpg, readgif, splitppm.

 readimagefile    Read an image file of any supported image format.
                  The currently supported formats are:
                  PGM/PPM (both ascii and binary), FI, JFIF, IMG and GIF.

 Created:  August 1998
 Modified: June   2000 by Etienne Grossmann <etienne@isr.ist.utl.pt>
           Accepts GIF and IMG (octave's image format. indexed IMG's are
           converted to gray or rgb)
 Version: 1.0

Listing of function file tmp_for_tar/imgio/readimagefile.m

## [im, isPpm, maxval] = readimagefile(fname, force_gray)
##
## fname      : string : name of image file.
## force_gray : flag   : (opt) if true, the returned image is a gray level
##                       image, even if the file contained a color image.
##                       (default: false) 
## im         : matrix : an image.  Note, that if force_gray == false, the
##                       image might by a PPM representation of the image.
## isPpm      : flag   : 1 : `im' is in PPM format.
##                       0 : `im' is a graylevel matrix.
## maxval     : int    : Maximum luminosity level (usually 255)
## 
## See also: readpnm, readfi, readjpg, readgif, splitppm.
##
## readimagefile    Read an image file of any supported image format.
##                  The currently supported formats are:
##                  PGM/PPM (both ascii and binary), FI, JFIF, IMG and GIF.
##

## Copyright (C) 1998 Ariel Tankus
## 
## This program is free software.
## This file is part of the Image Processing Toolbox for Octave
##
## This program is free software; you can redistribute it and/or
## modify it under the terms of the GNU General Public License
## as published by the Free Software Foundation; either version 2
## of the License, or (at your option) any later version.
## 
## This program is distributed in the hope that it will be useful,
## but WITHOUT ANY WARRANTY; without even the implied warranty of
## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
## GNU General Public License for more details.
## 
## You should have received a copy of the GNU General Public License
## along with this program; if not, write to the Free Software
## Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
##
## Author: Ariel Tankus <arielt@math.tau.ac.il>
## Created:  August 1998
## Modified: June   2000 by Etienne Grossmann <etienne@isr.ist.utl.pt>
##           Accepts GIF and IMG (octave's image format. indexed IMG's are
##           converted to gray or rgb)
## Version: 1.0

function [im, isPpm, maxval] = readimagefile (fname, force_gray)

if (nargin < 2)
    force_gray = 0;
end

fname = file_in_path(IMAGEPATH, fname);

if isempty (fname),
  error ("readimagefile : Can't find file '%s'",fname);
##  im = [];
##  isPpm = 0;
##  return
end

[fid, magicnum] = getmagicnum(fname);
fclose(fid);

if (strcmp(magicnum, "P2") | strcmp(magicnum, "P5"))
    ## PGM
  [im,isPpm,maxval] = readpnm(fname);
elseif (strcmp(magicnum, "P3") | strcmp(magicnum, "P6"))
    ## PPM
  [im,isPpm,maxval] = readpnm(fname);
  if (nargout > 1)
    isPpm = 1;
  end
				# jpeg    
elseif (strcmp(magicnum, "ÿØ"))
  [im, isPpm,maxval] = readjpg(fname);

elseif (strcmp(magicnum, "FI"))
    im = readfi(fname);
    maxval = 0 ;
    isPpm = 0 ;
elseif (strcmp(magicnum, "GI"))
  ## error("Probably a GIF file. Currently not supported.");
  [im,isPpm,maxval] = readgif (fname);

				# Probably IMG
elseif (strcmp(magicnum, "# "))
  [im,map] = loadimage (fname);
				# Gray
  if all ((map(:,1)==map(:,2)) & (map(:,1)==map(:,3)) ),
    isPpm = 0 ;
  else
    isPpm = 1;
  end
#  				# Gray
#    if all ( (map(:,1)==map(:,2)) & (map(:,1)==map(:,3)) ),
#      im = ind2gray (im, map);
#      isPpm = 0 ;
#    else				# Rgb
#      [R,G,B] = ind2rgb (im, map);
#      im = reshape ([R;G;B], rows(R), 3*columns(R)) ;
#      isPpm = 1 ;
#    end
#    maxval = 1 ;
				# jpeg
else
    error("Unknow file type encountered.");
end

if isPpm && force_gray,
  [r,g,b] = splitppm(im);
  im = (r + g + b) / 3;
  isPpm = 0 ;
end

endfunction